1. Field of the Invention
The present invention relates to a liquid crystal display. More particularly, the present invention relates to a liquid crystal display using a laser as a light source and a method for controlling brightness of an image on the liquid crystal display.
2. Description of the Related Art
Typically, a liquid crystal display (LCD) displays a desired image on a screen by adjusting transmittance of light supplied from a backlight unit to a liquid crystal display panel. The liquid crystal display panel has a plurality of liquid crystal cells arranged in a form of a matrix and a plurality of control switches that switch a video signal to be supplied to the liquid crystal cells.
FIG. 1 shows a backlight unit for a conventional LCD 10. As shown in FIG. 1, a backlight unit comprises a light source 1 that emits light, a lamp housing 2 that surrounds the light source 1, a light guiding plate 3 that transforms light incident from the light source 1 into planar light, a reflection plate 4 located below the light guiding plate 3 that reflects light traveling in lateral and bottom sides of the light guiding plate 3 toward a top side of the light guiding plate 3, a diffusion plate 5 that diffuses light passing through the light guiding plate 3, a brightness enhancement film (BEF) 6 that disperses light emitted from the diffusion plate 5 and shields a reflection pattern, and a dual brightness enhancement film (DBEF) 7 that converges an angle of light emission.
Such a backlight unit employing the above-mentioned light guiding plate has an uncompetitive price due to its outsourcing of parts and complexity of manufacture, and also has a problem in that light may be leaked if the lamp housing does not cover lamps properly, and brightness is lowered as light passes through the light guiding plate. A direct-below typed backlight unit has a defect in that many lamps and various sheets must be used for prevention of light loss and uniform diffusion of light.
In addition, since a light source such as a cold cathode fluorescent lamp (CCFL) must be always lighted, a contrast of an image may be lowered by some leaked light even in a complete black signal.
Accordingly, there is a need for an improved liquid crystal display and method for controlling brightness of an image on the liquid crystal display.